ZINC SELENIDE SUBSTRATES FOR BLUE LASERS

Crystals of ZnSe are needed as substrate wafers for the growth of 11-VI epitaxial structures for blue and green LEDs and lasers. The matching of lattice constants, thermal expansion coefficients and energy bands, as well as chemical compatibility, provide a strong incentive to use native substrates. Classical growth methods all suffer from problems; in some cases, quality is high but cost, resistivity and fragility are also high. Melt growth is used for all other high volume semiconductors, presumably because the high rate of growth leads to reasonable cost. However, ZnSe has a phase transition close to the melting point. Thus, we propose a slightly lower temperature growth process that combines the speed and composition versatility of melt growth with the features of other low temperature processes. Early results have shown that significant volumes of twin-free ZnSe can be grown. Conductivity without annealing has also been seen. We expect that this process will be capable of meeting the Phase II goal of high n-type doping densities.